1. Field of the Invention
The present invention relates to a keypad device of an electronic product, and more particularly, to a keypad device with a modularized backlight module.
2. Description of the Prior Art
A keypad with backlight function of an electronic device is widely used currently. Keys of the keypad can emit light when being triggered so that a user can press right keys in a dark situation. Please refer to FIG. 1. FIG. 1 is a perspective front view of a keypad device 1 in the prior art. The keypad device 1 includes a plurality of keys 11, and a plurality of light emitting diode (LED) lamps 12 for emitting light so as to assist the user in using the keys 11 in the dark situation.
As shown in FIG. 1, the LED lamps 12 are distributed among the keys 11. However, it has a disadvantage of light nonuniformity because light emitted from each LED lamp 12 weakens with increasing emitting distance accordingly so that visual quality is reduced.
An assembly backlight module substitutes for the simply LED lamp to solve the above-mentioned problem. A light guide plate of the backlight module is for guiding light so as to increase luminance and light uniformity of a display panel. Please refer to FIG. 2. FIG. 2 is a diagram of a light guide plate 22 in the prior art. A light source 21 is disposed on a lateral side of the light guide plate 22. Light emitted from the light source 21 enters the light guide plate 22 laterally and reflects inside the light guide plate 22 repeatedly for proceeding in a direction opposite to the light source 21. The light can scatter so as to emit out of a surface of the light guide plate 22 by a pattern 23 formed on the light guide plate 22. The pattern 23 on the light guide plate 22 can be formed at a printing method or an etching method.
Please refer to FIG. 3. FIG. 3 is a diagram of the light guide plate 22 utilized in a mobile phone in the prior art. The light guide plate 22 can be utilized in a backlight module of a keypad of the mobile phone. An Adhesive 33 is disposed on a side with the pattern 23 of the light guide plate 22 for adhering a dome sheet 34. A surface 341 of the dome sheet includes adhesive material for adhering a metal dome 35 so as to connect with a printed circuit board (PCB) 36. The manufacturing method of layer disposition causes difficulty in manufacture, and the mobile phone can not form in a thin type.